Apparatus for drilling bores deviating from existing well bores



APPARATUS lFIOR DRILLING BORES DEVIATING FROM EXISTING WELL BORESFiledMay 29, 1943 3 Sheets-Sheet l UM W,

{Ja/MMM@ @www J. A. ZUBLlN Dec. 7, 1943.

APPARATUS 'FOR DRILLING-BORES DEVI-ATING FROM EXISTING WELL BORES FiledMay 29, 1943 3 Sheets-Sheet 2 .A I f i\ 0 Dec. 7, 1943. 2,336,338

APPARATUS 'FOR DRILLING BoREs DEVIATING FROM EXISTING WELL BoREs J. A.ZUBLIN FledMay 29, 1943 5 Sheets-Sheet 3 Jn-UC n Kot Patented Dec. 1,1943 y APPARATUS FOR DRILLING BRES DEVI- ATING FROM EXISTING WELL BORESJohn A. Zublin, Los Angeles, Calif. Application May V29, 1943, SerialNo. 89,0510

10 Claims. (Cl. Z55-1.6)

This invention relates to the art of drilling well bores which primarilyriginate and terminate within the oil sand an which deviate stronglyfrom the axis of an existing well bore for the purpose of tapping oilsands too distant from the well for drainage by the well itself.

The present application constitutes a continuation-in-part of each of myearlier led applications Serial Nos. 423,225 and 423,227, filed December16,1941.

Present methods of drilling holes which deviate from the axis of anexisting well are conned mainly to two methods; rstly, to exert withwhlpstocks, knuckle Joints or similar deviating devices, a sidewardspressure on the bit attached to the customary string of drill pipeusedfor drilling oil wells to such an extent as to deviate this bit andpipe from the original axis of the hole; secondly, to attach a veryexible section at the bottom of regular drill pipe, this flexiblesection being of the nature of metallic flexible hose or jointed shortindividual sections enabling the drilling of lateral holes at rightangles to the 'well bore with a very sharp turn from the vertical axisof the well. a

Of the two methods, only the rst is in practical use for the purpose ofreaching underground sources of oil which are not vertically under thederrick of the well. This inclined drilling, however, proceeds, becauseof the stiffness of the regular drill pipe, only at very small angleswith minimum radii of curvature of more than 500 feet, making itimpossible to confine these deviating holes to the thickness of theaverage oil sand. Deviation, therefore, must start above the oil sand,calling forcasing and cementing and all other expensive requirementsnecessary in the drilling of standard vertical holes. The second methodhas the opposite disadvantage of being too flexible, making itimpossible to obtain a bore in a dened horizontal and vertical directionbeyond a certain distance from the well, since the extreme flexibilitydoes not give the bit sufficient rigidity to drill the oil sand and tomaintain a predetermined direction.

The present invention combines to some extent the advantages of bothmethods, eliminating at the same time their weaknesses, making it there-`fore practical to drill side holes from an existing well whethervertical or not, the side hole start. ing fromthe original hole withinthe oil sand at any place, and extending in any direction with a curveof any desired radius, in some instances as small as feet, thoughusually the curve will have a radius 'from 10 to 100 feet. Drilling ofthis curved hole can be stopped at will and continued with a straighthole. Alternating of curved hole and straight hole at will is entirely ffeasible in any direction and at any angle, thus enabling the drillingofsubstantially horizontal holes from a vertical bore penetrating an oilbit which is slightly smaller in diameter than the l bit will provide aguide for the bit itself. A permanently curved guide of this characterwill force a bit to drill a curved hole, and a permanently straightguide of this character will force -a bit to drill a straight hole. Ihave discovered that when a curved hole deviating from a straight holels desired, this can be accomplished by introducing a flexible resilientcurved guide forcibly into the straight well bore, said curved guidebeing flexible enough to allow it to be pushed into the straight hole.If it be desired to drill a straight bore from an existing curved bore,a flexible resilient straight guide is forcibly inserted into the curvedbore. It now the bit is placed at the point where the deviating hole isto be started and rotated without rotation of the drill guide, theresiliency of the long tubular guide forcibly flexed by entering theoriginal hole exerts a very considerable side pressure on the l4figuration.

drilling bit .rotatably connected with it, causing it to dig immediatelyinto the side of the wall at the point of contact. ,If the tubular guideis now lowered, the bit will continue to. drill sidewardly but alsodownwardly, the guide following the bit as drilling progresses. Theresiliency ofv the forcibly flexed guide will continue to exert a sidepressure on the bit until the guide has reached its tensionless orunstressed state, thus assuming its normal unstressed longitudinal con-For example, when using a drill guide having a normal unstressed curvedconfiguration, the bit will be forced to continue drilling acorrespondingly curved hole under the side pressure of the guide exertedon it.

Now, when using a curved drill guide of the invention, if an amount ofcurved hole has been made substantially equal in radius to theradius ofthe curved guide in tensionless condition, the relation between curvedhole and curved guide will be reversed to the point that whereas in thebeginning the guide forced thev bit to drill a curved hole, said curvedhole now causes the relaxed guide to continue along this curve as longas desired. In other words, a guide of va. radius of 25 feet and alength of 20 feet will continue to guide the bit in the drilling of ahole lof the same radius even after the length of this drilled hole hasexceeded the -ioot length of the curved* guide.

It is further clear that if the bit is withdrawn from the hole and thecurved guide immediately behind the bit is replaced with a flexibleresilient straight guide of the invention, this resilient straight guidewill be forcibly flexed on entering the curved bore and will exert onthe bit opposite side pressure, forcing the bit to discontinue drillinga curved hole and to drill from there on a straight hole. The deviationof bores is therefore reversible from a straight hole to a curved holeat will, at any point and in any direction.

Through use of the present invention it is possible to drill a side holeout of anzexisting vertical hole, as well as to drill a second side holeout of the first side hole in`the desired direction,

makingit possible to supply a well with a number of side holes whichleave the vertical bore of the well at different points, these sideholes having additional side holes, and thus forming a ramiflcation ofholes around the well which will eilectively drain all the oil whichpossibly can be l 'recovered from the area allotted to this well.

Although this invention is primarily designed to drill deviating holesout of an existing open hole, it is, however, possible to use the sameprocedure in drilling windows through the casing within a well, thesuccessful performance being only a matter of sufllcient lateralpressure of the resilient curved guide.

The invention is also applicable to the obtaining'of side wall samplesfrom a well bore. It becomes a simple matter to attach a conventionalcore head to the resilient guide and to utilize the entire device as ii'proceeding to drill a side hole, but stopping the operation of thedevice after the head has advanced sufdciently to take BCOle;

With the deciencies of present day apparatus and methods in mind. itbecomes a primary object of the present invention to provide improvedapparatus for drilling a well bore deviating from an existing well bore.

It is a more specific object of the invention to provide a ilexibleresilient drill guide having 9 normal unstressed longitudinalconfiguration corresponding approximately to the desired coniigurationof the deviating bore to be drilled from an existing bore and which iscapable when flexed to enter an existing bore of storing sufilcientpotential energy to forciblypres; a drill bit carried at the -,end ofthel guide tn follow a path substantially conforming to che normalunstressed conilguration of the drill guide.

A further object .of the invention is to provide Aapparatus fordrillingr a curved bore deviating from an existing straight bore aswellas apparatus for drilling a straight bore deviating from an existingcurved bore.

Still a further object of the invention contemplates the provision offlexible resilient drill guides adapted to Ibe flexed when positioned inan existing well bore and to do useful work in guiding a drill bitduring return from a ilexed to an unflexed state which can be coupled toa drilling string and bit either in such manner as to rotate with thedrill string and bit or in such manner as to permit independent rotationof the' drill bit.

side elevation of that form of the invention in which the flexibleresilient guide is of a normallycurved longitudinal conguration.

Figure 2 is a view illustrating the flexed coniiguration of the drillguide of Fig'. 1 when disposed in an existing straight well bore.

Figure 3 is a view illustrating the configuration of the curveddeviating bore resulting from the employment of the drill guide of Fig.1.

Figure 4 is a somewhat diagrammatic side elevational view of that formof the invention in which the flexible resilient drill guide has anormally straight longitudinal configuration.

Figure 5 is a. view illustrating the disposition of the normallystraight drill guide of Fig. 4 in a curve'd bore previously drilled withthe curved drill guide 0f Fig. 1.

Figure 6 is a view illustrating` the mode of operation by which astraight continuation of a curved bore is drilled employing the drillguide of Fig. 4.

Figure 7 is of one form of rotary drill bit that may be employed inconjunction with certain modiiications of the invention.

Figure 8 is a cross sectional view on the line 8-'8 of Fig. 7,specifically illustrating a flanged inner hose molded into the tube.

Figure 9 is a detailed view-of one form of straight drill guideconforming to the invention.

Figure 10 is a detail view similar' to Fig. 9 with parts broken away anddetails shown in' cross section of a further modification of the invernVtion.

Figure 13 is a detailed view of a device adapted to be employed intaking side wall samples shown in association with one form of theinvention.

Referring first to the form of the invention shown in Figs. 1 to 3, theelongated flexible resilient drill guide of normally curvedconfiguration is generally indicated at I and is helically slotted asindicated at 2. lThe pitch of the helical slot 2 may increase from theends of the drill guide I toward the center thereof and is preferably atall points greater than the external diameter ofthe tube. Thetube I isadapted to carry a suitable drill bit 3 at its lower end and to beconnected into a drill string at its upper end 4. In the presentinstance, it is shown as connected to a second flexible resilient member5 which may have a normally straight longitudinal configuration.

Since it is desired to have the guide take a curve which is of uniformcurvature throughout and for a curved guide to straighten from a similarcurve, it is necessary that the equivalent sinuous beam be of varyingcross section from end to end. A beam of this description is known as a.uniform strength beam. In accordancewith the present invention, it isnecessary that the guide be stiffer in the center than at the ends. Thishas been accomplished by varying the pitch of thehelical slot so that itis greater at the intermediate portion of the. guide than near the endsthereof.

In Fig. 2, the normally curved flexible resilient a detailed view partlyin section guide I is shown in the iiexed position that it is complelledto assume upon entering the straight well bore 6. In this case, the bit3 is shown in position to commence the drilling of a deviating bore at'the point 1. It will be appreciated that in the ilexing of the drillstem I from its normally unstressed curved longitudinal conguration, asshown in Fig. l, to the position that it assumes in the straight wellbore of Fig. 2, there is stored up in the drill guide very substantialpotential energy available to do work when the drill bit 3 is rotatedand advanced.

In Fig. 3, the flexible resilient drill guide I is shown in the positionthat it assumes when the initial curved deviating bore 8 has beendrilled from the existing vertical well bore 6. It will be understoodthat this drilling is accomplished by holding the ilexed drill guide Iin the position shown in Fig. 2 against rotationwhile rotating andadvancing the drill bit 3. In this way the potential energy stored inthe drill guide I is expended in pressing the drill bit 3 sidewardlyagainst the wall of the existing well bore 6 and in guiding the same inthe drilling of a deviating bore having a conguration correspondingsubstantially to that of the relaxed and unstressed normal conilgurationoi' the drill guide I.

Since the direction and character of the deviating bore depend upon thecharacter and normal unstressed longitudinal conguration of the drillguide, it will be appreciated that a drill guide having a congurationconforming substantially to that of the desired deviating bore will beselected for any given operation. It will likewise be appreciated thatwhile a normally curved resilient drill guide such as illustrated at I'in withintherangeofapproximatelyZOfeetto 100 feetwithout the metal ofthe guide tube beyond its elastic limit. Because of-this property, drillguides conforming to the present .invention are possessed of long lifein repeated use.

Another operation not speciiically -disclosed in the drawings canbeperformed with the drill guide I.` For example, if, after the initialcurved Fig. 1 may be used to drill a deviating curved bore, a normallystraight drill guide such `as the one indicated at 9 in Fig. 4 may beused in drillbit I0 are shown in Fig. 5," the guide 9 will, if K* heldagainst rotation during further advancev vand rotation of the drill bitI0, so guide the 'drill bit that it will drill a straight continuationof the curved bore as specifically illustrated in Fig. 6.

` It will be understoodthat the deviating bore as shown in Fig. 6isdrilled by ilrst employing the curved drill guide I of Fig. 1 toinitiate the curved -bore and by thereafterv substituting for the curvedguide I the normally straight drill guide l. Asecond normally straightflexible seetion II is shown as connected to the upper ena of thestraight guide s in Figs. 5 and s.

ilexible drill guide IY against rotation, further drilling is effectedby rotation of the exible drill guide I, a continuing straght bore canbe drilled, which is, however, of substantially greater diameter thanthe bit. 'Insuch operation, the rotation ot'the curved guide causes theproduction of an initially tapered bore which eventually becomescylindrical. The reason for the straightness of the bore drilled byrotation of the curved drill guide is the fact that rotation of thecurved guide neutralizes the eect of the curvature thereof. Theenlargement of the straight continuing bore so drilled is occasioned bythe continuing side pressure exerted on the bit by the rotating curvedguide. This operationv has one material advantage; namely, that it ispossible to initiatea curved bore deviating from an existing straightbore and effect the drilling of a straight extension of Vsuch curvedbore with the same equipment and without removing the drill string andbit from the well.

Coming now to some of the more detailed aspects of the invention, thereis shown in Fig. 7 a exible resilient drill guide I2 conforming to theinvention within which there is disposed, preferably by molding therein,an inner imperfoi'ate exible hose I3, which' in this particui larconstruction is provided with a helical compressible ange Il adapted toextend outwardly through the helical slot I5 of the flexible guide tubeI2. In the form of the invention shown in Fig. '1, the inner tube I3 andthe outer tube I2 are, of course, not capable of independent rotation.It will be realized that because of the relative softness of rubber ascompared to the metal of which the guide I2 in made, the helical layer yof rubber I l within the slot I5 does not offer too great resistance tothe ilexing of the tube I2, the helical rubber layer Il merelycompressing 'and stretching under the iniluence of bending of the tubewhich causes the slot I 5 to open and close. The turbine driven rotatingbit shown in Fig. 7 is of a typev similar to that described in my PatentNo. 1,859,948, and has been found highly suitable Ior turbine drivesbecame of the gear reduction eiect described in said patent. -In thiscase the stator IC of the turbine is threadedly received inthe lower endof the resilient iiexible The normally straight ilexible resilient drillbic guide a must be perfectly resuient in bendingffl'ma straight line'to the are of the curved boi-'e'.and from this are to a straight linewithout stressing the metal o! the tube beyond its elastic limit.Likewise, the normally curved flexible 'resilientdrill guide of Fig. 1must be perfectlyA resilient in bending from its normally curvedconfiguration to substantially a straight line without stressing. themetal of the tube beyond its elastic limit.

` It will thus be apparent that either the straight or the curved formof the guide is capable of passing through both a straight well bore anda curved well bore having a radius pf curvature guide tube I2 and issecured'by a center pin I1 to the rotor Il which is attached to the bitindicated generally at I9. One or more rows of,

balls 2l are located in races on the stator Il and rotor Il. These ballsserve theduai purpose of the stator and rotor together and providing ameans for minimizlng friction between annular-ly surrounding the pin I1.These open- I ings 2l are defined by guides or vanes 22. These vanes arehelically disposed around the center pin I'I so that they impart'to thedrilling iluid a rotational velocity. it passes them. 'l'.'he rotor'Ilofthe turbine is likewise provided with vanes -23 also helicallydisposed about the axis of the turbine. I'hese vanes are directed in theopposite direction from the vanes 22 on the stator similarly to thevanes in any axial ow turbine. In this manner drilling fluid passingthrough .the hose I3 is delivered through the vanes in the stator andgiven a rotational velocity causing a reaction on the blades of therotor, exerting a. torque thereon which will drive the bit withoutrotation of the guide tube l2. While in Fig. 7, I.have illustrated a.specific form of bit, it will beappreciated that any suitable type ofbit may be used. It will also be appreciated that the specificconstruction of the flexible metal tube I 2 and inner hose I3 disclosedin Figs. 7 and 8 may be used in any case where relative rotation betweenthe inner fluid conveying hose and the outer flexible metal tube is notrequired.

Coming-next to the features disclosed in Figs. 9, l and 11, the flexibleresilient drill guide 24 is shown as carrying a rotating drill bit atits lower end and provided with threaded means 26 at its upper end forcoupling into a drilling string. The helical slot 21 in this instance isillustrated as of varying pitch, the pitch of the slot increasing fromthe ends of the tube 24 toward the center thereof and being in allinstances greater than the external diameter of the tube 24.

By reference to the detailed showing in Fig. l0, it will be noted thatthe inner hose 28 is mounted for free rotation within the flexible tube24 and that the hose 28 is connected at its lower end to the bit 25,whereby the bit 25 may be driven through the medium of the hose 28. Itwill be understood that the hose 28 in this form of the inventionperforms the dual function of conveying drilling fluid from the drillingstring to the bit and permitting rotation of the bit without rotation ofthe guide 24.

A coupling 28 isl shown for use in coupling the flexible resilient tube24 into a drilling string. In Fig. 10, coupling 29 interconnectsflexible drill guide 24 with a second flexible section 38. There is alsoshown a. suitable coupling for interconnecting sections of the hose 28.In this case, the opposed ends of the sections of the hose 28 carrycomplementary threaded coupling elements 3| and 32 interconnected at 33.In order to prevent axial movement of the hose 28 within the guide 24,the interior of the coupling 29 and the exterior of the couplingelements 3l and 32 are provided with races withinwhich balls 34 can runto form bearings which prevent axial movement of coupling elements 3|and 32 with re- Aspect to the coupling 28. These balls also serve toreduce friction on relative rotation of the hose 28 and the flexibletube 24. Of course, it will be realized that these balls 34 must beinserted after the tubes 24 and 3|) are coupled together and the hosecoupling elements 3l and 32 coupled together. To permit of suchinsertion, a small tapped hole 35 is provided opposite each raceextending through thej coupling 28. Threaded couplings 36 are providedto retain the balls in place after they have been inserted. It will beobserved that balls 31 similar to the balls 34 are positioned in racesformed in the tube 24 and the bit shank to insure free rotation of thebit '25 andv hose 28 relative to the outer flexible resilient metal tube24.

In the construction shown in Figs. 9,10 and 11, it is possible to holdthe drill string including the flexible resilient guide 24 againstrotation while rotating and advancing the drill bit. It is, of course,also possible. in the event such operation is desired, to rotate thedrill string either at the same orl at a different speed of rotationthan that at which the drill bit is driven.

In Fig. 12, there is illustrated a modified form of the invention moreespecially adapted to those conditions where flexing of the drill guidein a single plane vis desired. In this case, the flexibleresilient metaltube 38 is provided with the staggered transverse slots 39. To insuregreater stiffness of the tube at the center than near the ends, theslots 39.are spaced farther apart near the center of the tube than nearthe ends thereof. 'I'he mode of operation of the flexible resilientdrillguide of Fig. 12 is generally comparable to that of the helicallyslotted drill guide with the exception that i't is primarily adapted toflex in one plane. In this case, the hose 48 is interconnected by thecoupling 4I to the tube 38 so as to rotate with the tube-38. It will beappreciated, however, that the relationship between the hose 40 and tube38 may be made comparable to that existing between the hose 28 and thetube 24 as illustrated in Fig. 10;

It is often desirable to take a side wall sample from an existing wellbore, and in Fig. 13 I have illustrated the adaptation of the inventionto such use. In this form, a suitable core head 42, which comprisesessentially a rotary bit so formed as to leave a core as it cuts intothe formation, is rotated by means ofthe hose 43 disposed interiorly ofthe outer flexible resilient metal 'drill guide 44, which in thisinstance is held against rotation while the core head 42 issimultaneously rotated and advanced to take the sample. The flexibleresilient guide 44 serves to A cause the core to be taken at an angle ofthe side Wall of the bore within which the flexible resilientguide 44has been forcibly introduced.

The foregoing description is given by Way of exempliflcatfon of theinvention and not in limitation thereof, the scope of the inventionbeing that setl forth in the appended claims.

WhatIclaim is:

1. A well drill bit guide for guiding a rotating drill bit in drilling awell bore deviating from an existing well bore comprising a flexiblemetal tube of high resiliency having a normal unstressed longitudinalconfiguration corresponding approximately to the desired longitudinalconfiguration of the deviating Well bore and from `which conilgurationsaid tube must be forcibly flexed to enter the existing well bore, saidtube being capable of passing through both a straight Well bore and acurved well bore having a radius of curvature within the range of from20 to 100 feet without stressing the metal o-f the` tube beyond itselastic limit, the resiliency of said tube when flexed to enter theexisting well bore being adequate to store sufllcient potential energyto forcibly guide a rotating drill bit from the existing bore in a pathconforming to the unflexed configuration of said tube.

2. A well drill bit guide for guiding a drill bit in drilling a wellbore deviatixg from an existing well bore comprising a slotted flexiblemetal tube of high resiliency having a normal unstressed longitudinalconfiguration corresponding approximately to the desired longitudinalconfiguration of the deviating well bore and from which configurationsaid tube must be forcibly flexed to enter the existing well bore, saidtube being capable of passing through both a straight wel1 bore and acurved well bore having a radius of curvature withinpthe range of from20 to 100 feet Without stressing the metal of the tube beyond itselastic limit, the resiliency of said tube when flexed to enter theexisting well bore being adequate to store suillcient potential energyto forcibly guide a rotating drill bit from the existing bore in avpathconforming to the unilexed configuration of said tube, a flexible hosemounted within said tube for conveying iiuid therethrough and means forcoupling said tube to a well drilling string.

3. A well' drill bit guide for guiding a rotating drill bit in drilling.a well bore deviating from an existing well bore comprising a tube ofmaterial of high resiliency having a slot in its wall extendinghelically around and along the tube to render the tube flexible tobending, the pitch of said helical slot being greater than the outsidediameter of said tube, said tube having a normal unstressed longitudinalconfiguration corresponding approximately to the desired longitudinalconfiguration of the deviating well bore and from which configurationsaid tube must be forcibly ilexed to enter the existing Well bore, saidtube being capable of passing through both a straight well bore and acurved well bore having a radiusoi curvature within the range of from 20to 100 feet without stressing the metal of the tube beyond its elasticlimit, the resiliency of said tube when flexed to enter the existingwell bore being adequate to store sumcient potential energy to forciblyguide a rotating drillbit from the existing well bore in a pathconforming-t the unilexed configuration of said tube.

4. A well drill bit guide for guiding a drill bit in drilling a, wellbore deviating from an existing well bore comprising a tube 4of materialof high resiliency having a slot in its wall extending helically aroundand along the tube to render the tube exible to bending, the pitch ofsaid helical slot varying from a. minimum near the ends of the tube to amaximum at the center of the tube and the pitch throughout a substantialportion of the length of the tube being greaterthan vthe outsidediameter of the tube. said tube having the existing bore in avpathconforming to the unilexed configuration of said tube, a flexible hosemounted within said tube for rotation therein, means for coupling saidhose to a drill bit, and means for coupling said tube to a well drilling string.

6. A well drill bit guide for guiding a drill bit in drilling a curvedwell bore deviating from an existing-straight well bore comprising aexible metal tube of high resiliency having a normally curvedconfiguration corresponding approximately to the desired longitudinalconiguration of the deviating curved well bore and from whichconfiguration said tube must be forcibly flexed to enter the existingstraight well bore, said tube being'capable of passing through both theexisting straight well bore and a curved well bore having a radius ofcurvature within the range of from 20 to 100 feet without stressing themetal of the tubev beyond its elastic limit, the resiliency of said tubewhen iiexed to enter the existing straight well bore being adequate tostore sufficient potential energy to forcibly guide al rotating drillbit from the existing bore in a path conforming approximately to thenormal uniiexed configuration of said tube.

7. A well drill bit guide. for guiding a drill bit in a well boredeviating from an existing well bore comprising a tube of metal of highresiliency having transverse slots in staggered relationship indiametrically opposed walls thereof to render the tube flexible tobending in one plane, said tube having a normal unstressed longitudinalconfiguration corresponding approximately to the desired longitudinalconguration of the deviating well bore and from which configuration saidtube must be forcibly iiexed to 'enter the existing well bore, said tubebeing capable of passing -through both a straight well bore and a curvedg well bore having a radius of curvature within the range of from 20.to100 feet without stressing the metal of the tube beyond its elasticlimit,

a normal unstressed longitudinal configuration correspondingapproximately tothe desired longitudinal conilguration ofthe deviatingwell bore and from which coniiguration said tube must be forcibly flexedto enter the existing well bore, said tube being capable of passingthrough both a straight well bore and a curved well bore having a radiusof curvature within the range of from 20 to 100 feet without stressingthe metal of the tube beyond its elastic limit,the resiliency of saidtube when flexed to. enter the existing well bore being adequate tostore sufficient potential energy to forcibly guide -a rotating'drillbit from the existing bore in a path conforming to the unflexedconfiguration of said tube. I

5. A well drill bit guide for guiding a rotating drill bit in drilling awell bore deviating from an existing well-bore comprising a slottedflexible metal tube of highreslliency having a normal unstressedlongitudinal configuration .correspending approximately to the desiredlongitudinal conguration of the -deviating well bore and from whichconfiguration said tube must be forcibly ilexed to enter the existingwell bore, said tube being capable of passing through both a straightwell bore and a curved well bore having a radius oi' curvature withinthe range of from 20 to 100 feet without stressing the metal 4oi' thetube beyond its elastic limit, the resiliency of said tube when flexedto enter the existing well bore being adequate to store sumcientpotential energy to forcibly guide a rotating drill bit from u flexibleto bending, said tube having a nor.

the resiliency of said tube when iexed to enter the existing well borebeing adequate to store suiiicient potential energy to forcibly guide arotating drill bit from the existing well bore iny I the uniiexedconguration the pitch of said slot being greater than the cutsidediameterv oit said tube, aid tube having a no1-many straight mngitudinficonguranon from.

which configuration it must be forcibly exed to enter the existingcurved well bore, said tube being capable of passing through both astraight well bore and a curved well bore having a radius oi curvaturewithin the range'of from 20 to 100 feet without stressing the metal ofthe tube beyond its elastic limit, the resiliency of said tube whenflexed to enter the existing curved well bore being adequate to storesufilcient potential energy to forcibly guide a rotating drill bit fromthe existing curved bore in a straight path mal-unstressed longitudinalconfiguration corresponding approximately to the desired longitudinalconilguration of the deviating well bore and from which conilgurationsaid tube must be forcibly exed to enter the existing well bore, saidtube being capable of passing through both a straight well bore and acurved well bore having a radius. of curvature within the range of from20 to 100 feet without stressing the metal of the tube beyond itselastic limit, the resiliency of said'tube when flexed to enter theexisting well .bore being adequate to store suflicient potential energyto forcibly guide a rotating drill bit from the existing bore in a pathconforming to the uniiexed conguration of said tube, a`tlexible hosemounted within said tube for conveying fluid therethrough, said hosehaving a compressible flange extending helically. around and along itsouter surface, said ange lying vwithin the said tube t0 a well drillingstring. f

10. A well drill bit guide for guiding a drill bit in drilling a curvedwell bore deviating from an existing straight well bore comprising aiiexible metal tube of high resiliency having a normally curvedconfiguration having a radius of curvature within the range of from 10to 100 feet and corresponding approximately to the desired longitudinalconilguration of the deviating curved well bore and fromwhichconguration said tube must be forcibly flexed to enter the existingstraight well bore, said tube being capable of passing through theexisting straight well bore without stressing the metal of the-tubebeyond its elastic limit, the resiliency of said tube when iiexed toenter the existing straight well bore being adequate to store.suiiicient potential energy to forcibly guide a rotating drill bit fromthe existing bore in a path conforming approximately to the normaluniiexed configuration of helical slot in said tube, and means forcoupling 20 said tube..

JonN A. zUBLI.

